Age and injury finally caught up to Doug Weight, who retired from the NHL after a three-decade career that ended with a stint as Islanders captain.

The longtime captain who played for six teams announced his retirement Thursday at a Long Island hotel — about a slap shot away from the Nassau Coliseum — and accepted a job with the Islanders as an assistant coach and senior adviser to general manager Garth Snow.

Snow provided a bit of help to Weight, who bid a tearful farewell to the game he has played since he was a boy in Michigan. The 40-year-old paused several times during his prepared remarks to wipe his eyes with tissues provided by Snow, utter an audible sigh, and take sips of water as he tried to corral his increasing emotions.

“Saying goodbye and never going to play again in the league, it’s terrible,” Weight said. “It’s tough. It’s a sickening, sad feeling, but it’s also a new chapter to hopefully the greatest part of my life.”

Weight will work with the power play in his job as an assistant coach, and will help Snow in all aspects of personnel decisions whether it be free-agent signings, trades, or draft preparation. Weight thinks he will ultimately prefer the front-office side of the business.

“I would lean toward the management more than the coaching, but that’s just because I’m green and I don’t know,” he said. “In six months I could tell you, ’This is unbelievable. I love being behind the bench.’”

A back injury that cut his final season way short hastened the decision to end his playing career. Weight didn’t play after Nov. 17, having totaled two goals and seven assists. He played in only 36 games during the 2009-10 season and 53 games the previous season, his first with the Islanders.

“My health hasn’t come back as much as I’d like,” Weight said. “I still have some issues with my back and some soreness. If I felt 100 percent at the end of the season, I think I’d still be making this decision. I’m fulfilled and I feel good about it.”

In 1,238 NHL games with six teams, Weight had 278 goals and 1,033 points as one of the league’s top playmakers. He won a World Cup of Hockey championship for the United States, and was a three-time Olympian — winning a silver medal at the 2002 Salt Lake City Games.

His time with the Islanders made a lasting impression — Weight and his family have relocated from St. Louis to make their home on Long Island.

Weight, a four-time All-Star who ranks sixth in career points among American-born players, also will work with the NHL Network during the upcoming Stanley Cup finals.

All of that experience and insight convinced Snow to keep Weight within the organization that has missed the playoffs in four straight seasons and five of six.

“He has a wealth of knowledge and he has a great hockey mind that can help our team get to the next level,” Snow said.

Weight was flanked at Thursday’s announcement by Snow and Islanders owner Charles Wang. Also attending the news conference were family, friends and former teammates such as Bill Guerin, as well as some current Islanders.

“I knew the writing was on the wall and it was something I was going to have to face,” Weight said. “As sad as it is, I am very excited and fulfilled with my career. You can’t have regrets. I just wish I was healthy.”

Weight’s long career started with the Rangers in 1991. He spent parts of nine seasons with the Edmonton Oilers and became a star there, posting 104 points in 1995-96, including a career-best 79 assists. After a stay of three-plus seasons with the St. Louis Blues, Weight was dealt to Carolina in January 2006. He helped the Hurricanes win the Stanley Cup before returning to St. Louis in the offseason.

Weight was traded again by the Blues in 2007 to Anaheim and then signed with the Islanders the following summer. He joined longtime friend and fellow American star Guerin, who was the Islanders captain at the time.

Guerin and Weight were teammates often along the way, most notably in Edmonton, St. Louis and on U.S. teams. Their reunion in New York was short as Guerin was traded to Pittsburgh in March 2009 during their first season together. Weight took over as captain in the 2009-10 season.

“He could make plays, he could score goals, he could stand up for his teammates in the dressing room, he could take control at any time,” said Guerin, who ended his 18-year career in December. “You hope that what you bring rubs off on the guys who are going to be carrying the torch. I like to feel that I had some influence on some of the younger players, and I know for sure Doug did.”

Weight, chosen by the Rangers with the 34th pick in the 1990 draft, made his NHL debut in 1991. He began preparing for his post-playing career last season, spending some games behind the bench alongside coach Jack Capuano.

“Just the five games last season I stood on the bench helped me immensely,” Weight said. “It’s going to be an easy transition for me.”

Weight has served as a mentor to 2009 No. 1 overall pick John Tavares, the Islanders’ franchise player who has spent two seasons in the NHL. Tavares and forward Matt Moulson lived with Weight’s family as they got acclimated to the NHL.

“It’s going to be a little different, but we got a taste for it at the end of the year,” Tavares said. “He’s got great insight. With his experience and playing in big situations and crucial games, a lot of that stuff will come into play.”